Co-precipitation synthesis of nano-sized yttrium aluminium garnet (YAG) powders

Yttrium aluminium garnet (Y 3 Al 5 O 12 , YAG) is an important material used as a laser host and in phosphors. YAG powders are conventionally synthesized by solid-state reaction processing using Y 2 O 3 and Al 2 O 3 as starting materials. The solid-state reaction process usually requires high calcination temperatures to eliminate intermediate phases. The high calcination temperature inevitably leads to coarsening of the microstructure and, thus low sinterability of the synthesized powders. As a result, extremely high sintering temperatures are needed in order to obtain translucent or transparent YAG ceramics. Various wet-chemical methods have successfully reduced the calcination temperature of YAG powders. Both ammonium hydroxide and ammonium hydroxide carbonate were used as the precipitant for the synthesis of YAG powders via co-precipitation process. In this study, ammonium hydroxide carbonate was selected as the precipitant to produce Y 2 O 3 , Al 2 O 3 and YAG powders from the solutions of yttrium and aluminium nitrates via precipitation. The effect of the molar ratio between the precipitant and source salt on the yield and composition of the resultant yttrium and aluminium precipitates, and the evolution of the precursors of the resultant powders with calcination temperature were investigated.